The 123rd was not a Natl Gd activated for WWII. It was a newly-created unit to fill a space in the 33rd ID line-up before it deployed for war. Its personnel were overwhelmingly non-NG -- draftees with OR and RA cadres.
After the war, the NG in all states was reorganized with many and sundry changes. Some old units disappeared and new ones established. In teh 1946-1948 period, each state sent to the Pentagon a "State Plan" laying out the units they wanted and thought they could justify as essential to the natl defense. (Some of these, in retrospect, were ridiculously pumped up "wish lists", with no factoring in of realistic facilities, personnel, training areas, maintenance capabilities, etc.Just ploys for pork-barrel spending and slots for pols' pals.) .Illinois (like NY, Cal, and TX) wanted TWO Divs and basically squeezed the War Dept with political pressure. (Truman wanted his Universal Mil Tng plan which would put hordes of half-trained reservists on the street, ripe for NG recruitment and 1948 was an election year.) For a time, Illinois wanted/expected an Armored Div --- but that job was taken, by the 21st Armd Div (ORC), headquartered in Detroit with some elements in northern Ill. This "insult" just redoubled the political intrigue for a second ILNG Div, and the 44th was it. (NOTE: Unlike lower echelon units like Regts, Div HQs can be allotted and withdrawn from one state and given to another (Air NG units work the same way). The 44th pre-war was NY/NJ, but post-war NY got the 42nd and NJ did get an Armd Div.)
The 44th was in the southern half of the state and the 33rd in the north. When the Korean War came along, the 33rd was so bad that it could not be Federalized, so the rose was pinned on the somewhat-better 44th. In order to make the 44th fit, it got many individually-selected personnel from throughout the 33rd and other ILNG units. It went to Ft Lewis...but was judged as unfit and/or unready, as a unit, to serve overseas. As a result it was marked for demise, and that happened when it went off Federal duty in 1954. Out of the ashes, the best remnants (individuals and units) were merged into the 33rd (which was already being closely watched by Washington -- not to kill it off but to prop it up and pretend everything was fine Illinois). This is why the DUI changed,,,,though the post-1954 123rd was really a new and different outfit, with some pieces of the pre-1954 123rd rolled into it, it needed a cosmetic makeover. The latter 123rd largely descended from Cav/Armor units